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为了获得青藏高原冻土区天然气水合物地层的物性特征,采用岩石物理方法进行分析.首先,对青藏高原冻土区DK-1、DK-3和DK-4三个井孔制作了速度密度交会图,并比较了不同岩性水合物地层的差异.其次,基于DK-1和DK-4含水合物粉砂岩层段的测井数据,提取了水合物地层骨架的物性参数,包括纵波速度、横波速度、密度、体积模量和剪切模量.最后,依据水合物地层各主要成分的物性参数,建立了基于K-T方程的岩石物理模型和区分填充模式的岩石物理模型,将两类模型的速度曲线分别与实际地层数据进行了对比,并分析了模型与实际地层的近似程度,发现填充模式Ⅱ的水合物岩石物理模型更符合实际情况.冻土区水合物地层具有速度大、密度小的特征,砂岩水合物地层相比泥岩地层在速度和密度方面更具规律性,DK-4井孔165.80~166.35 m层段中水合物作为岩石骨架的一部分更能反映其物性特征.
In order to obtain the physical properties of natural gas hydrate stratum in the permafrost region of Qinghai-Tibet Plateau, the petrophysical method was used to analyze the characteristics.Firstly, the density density crossings of DK-1, DK-3 and DK-4 in the permafrost region of Qinghai- And compare the differences of different lithologic hydrate strata.Secondly, based on the well logging data of DK-1 and DK-4 hydrate-bearing siltstone intervals, the physical parameters of the hydrate strata skeleton are extracted, including the longitudinal wave velocity, Shear wave velocity, density, bulk modulus and shear modulus.Finally, based on the physical parameters of each major component of hydrate stratum, the petrophysical model based on KT equation and the petrophysical model of differentiated filling mode are established. Velocity curves are compared with the actual data of the strata respectively and the approximation degree of the model to the actual strata is analyzed. It is found that the physical model of the hydrate rock filling the mode II is more in line with the actual situation. The hydrate strata in the permafrost region are characterized by high velocity and low density Features, sandstone hydrate strata are more regular in velocity and density than mudstone strata, and the hydrate in the 165.80-166.35 m interval of the DK-4 wellbore is more capable of functioning as part of the rock skeleton Wherein enantiomerically physical properties.